@SilverJS - Which version of FreeNAS did you use when you created the "RaidZ2"?
Dude - I wish I could remember....one of the very early builds of FreeNAS 8. I'm talking 8.0.3 or something. I built my machine, and therefore created the pool, in 2011 - around August or so, if I recall.
Like I was saying in an earlier response - none of my research (obviously still insufficient, but still quite thorough, I thought!) at the time pointed to this naming convention being a problem. And, I wonder if I just never even checked this part of the GUI before (unlikely) or, if this is just one of those things like, say, the whole ashift debacle, where FreeNAS suddenly added support, or more precisely, started actually indicating errors that were present all along but simply not displayed.
In any case, I'll be re-creating my whole pool soon - in part because of this, also in part because of the ashift thing, and a few other things. I've built myself a reliable backup box, so when my hardware comes in for the main box, I'll start over, and name the pool "Tank".
Oh, and to DanB - thanks man! I appreciate the fix. I don't think I'll implement it though, as I'll use the re-creation of the pool as the time to re-map everything, change the shares, etc., etc....would rather do this only once, but good of it to be captured somewhere for posterity, in case someone else made the same dumb mistake I did. =)
EDIT : Dan, I know next to nothing about code, but should the third line not be "zpool" instead of "cpool"?